diff --git a/.github/workflows/run-pretrained.yml b/.github/workflows/run-pretrained.yml
index ee0753acc..710ca2603 100644
--- a/.github/workflows/run-pretrained.yml
+++ b/.github/workflows/run-pretrained.yml
@@ -50,6 +50,8 @@ jobs:
       - name: Install Python dependencies
         run: |
           python3 -m pip install --upgrade pip pytest
+          # numpy 1.20.x does not support python 3.6
+          pip install numpy==1.19
           pip install torch==${{ matrix.torch }}+cpu torchaudio==${{ matrix.torchaudio }}+cpu -f https://download.pytorch.org/whl/cpu/torch_stable.html
           pip install k2==${{ matrix.k2-version }}+cpu.torch${{ matrix.torch }} -f https://k2-fsa.org/nightly/